為某對象提供一種代理以控制對該對象的訪問阳似。即客戶端通過代理間接地訪問該對象叨粘，從而限制晤揣、增強或修改該對象的一些特性屋确。

• 靜態(tài)代理：需要定義接口或者父類纳击，被代理對象與代理對象一起實現(xiàn)相同的接口或者繼承相同父類
• 動態(tài)代理：
  • JDK代理：代理接口；
  • Cglib代理：不需要接口乍恐，而是創(chuàng)建子類

1评疗、靜態(tài)代理

package com.strife.pattern.proxy;

/**
 * 代理模式：靜態(tài)代理
 *
 * @author mengzhenghao
 * @date 2022/6/1
 */
public class StaticProxy {

    public static void main(String[] args) {
        //目標對象
        TeacherDao teacherDao = new TeacherDao();
        //通過代理對象調用被代理對象的方法
        new TeacherDaoProxy(teacherDao).teach();
    }
}

interface ITeacherDao {

    void teach();
}

class TeacherDao implements ITeacherDao {

    @Override
    public void teach() {
        System.out.println("teach方法被調用……");
    }
}

class TeacherDaoProxy implements ITeacherDao {

    private TeacherDao traget;

    public TeacherDaoProxy(TeacherDao traget) {
        this.traget = traget;
    }

    @Override
    public void teach() {
        System.out.println("teach()方法執(zhí)行之前");
        traget.teach();
        System.out.println("teach()方法執(zhí)行之后");
    }
}

2、JDK動態(tài)代理

package com.strife.pattern.proxy;

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;

/**
 * 代理模式：JDK動態(tài)代理
 *
 * @author mengzhenghao
 * @date 2022/6/1
 */
public class JdkProxy {

    public static void main(String[] args) {
        StudentDao studentDao = new StudentDao();
        ProxyFactory factory = new ProxyFactory(studentDao);
        IStudentDao proxyObject = (IStudentDao) factory.getProxyInstance();
        //class com.strife.pattern.proxy.$Proxy0 內存中動態(tài)生成了代理對象
        System.out.println(proxyObject.getClass());
        proxyObject.study();
    }
}

interface IStudentDao {

    void study();
}

class StudentDao implements IStudentDao {

    @Override
    public void study() {
        System.out.println("studying……");
    }
}

class ProxyFactory {

    private StudentDao target;

    public ProxyFactory(StudentDao target) {
        this.target = target;
    }

    /** 獲取代理對象 */
    public Object getProxyInstance() {
        return Proxy.newProxyInstance(target.getClass().getClassLoader(), target.getClass().getInterfaces(), new InvocationHandler() {
            @Override
            public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
                System.out.println("JDK代理開始");
                return method.invoke(target, args);
            }
        });
    }
}

3茵烈、Cglib動態(tài)代理

package com.strife.pattern.proxy;

import net.sf.cglib.proxy.Enhancer;
import net.sf.cglib.proxy.MethodInterceptor;
import net.sf.cglib.proxy.MethodProxy;

import java.lang.reflect.Method;

/**
 * 代理對象：Cglib動態(tài)代理
 *
 * @author mengzhenghao
 * @date 2022/6/1
 */
public class CglibProxy {

    public static void main(String[] args) {
        People people = new People();
        final People peopleProxy = (People) new PeopleProxyFactory(people).getProxyInstance();
        System.out.println(peopleProxy.walk());
    }
}

class People {

    String walk() {
        System.out.println("walking……");
        return "OK";
    }
}

class PeopleProxyFactory implements MethodInterceptor {

    private Object target;

    public PeopleProxyFactory(Object target) {
        this.target = target;
    }

    /** 返回代理對象 */
    public Object getProxyInstance() {
        //創(chuàng)建工具類
        final Enhancer enhancer = new Enhancer();
        //設置父類
        enhancer.setSuperclass(target.getClass());
        //設置回調函數(shù)
        enhancer.setCallback(this);
        //創(chuàng)建代理對象
        return enhancer.create();
    }

    @Override
    public Object intercept(Object o, Method method, Object[] args, MethodProxy methodProxy) throws Throwable {
        System.out.println("Cglib代理模式開始");
        return method.invoke(target, args);
    }
}

<!--Cglib依賴-->
<dependency>
    <groupId>cglib</groupId>
    <artifactId>cglib</artifactId>
    <version>3.1</version>
</dependency>